It is common knowledge that the creation of a number of objects quite often entails the recourse to junctions by means of tongue and groove joint pins, eccentric joint pins, and L-shaped elements, made of metal and other materials, adhesives, and so on.
The solutions outlined above have been adopted worldwide since time immemorial, even though they are often inadequate from an aesthetic point of view and, sometimes, they offer a poor resistance, particularly to transverse stresses.
Besides, these solutions do not allow a great freedom of junction among the parts, particularly when one wants to join together parts with angles other than right angles.